Method and apparatus for cementing a well

ABSTRACT

A method of cementing a well permitting a reduction in the degree of diameter reduction of casing or liners required, and not requiring excessively large initial conductor casing, is described. The method is characterized by provision of an enlarged wellbore and a novel liner structure which is adapted for expansion of a reduced diameter section thereof downhole, providing, before expansion of the section, unimpeded flow of fluid from the enlarged wellbore during cementing and close fit of the expanded section with the casing or preceding liner, after cementing is completed and expansion of the section. A novel well liner structure and novel well liner expansion means are disclosed.

FIELD OF THE INVENTION

This invention relates to a method for cementing a well and to apparatususeful in well cementing operations.

BACKGROUND OF THE INVENTION

In the conventional drilling of a well, such as an oil well, a series ofcasings and/or liners are commonly installed sequentially in thewellbore or borehole. In standard practice, each succeeding liner placedin the wellbore has an outside diameter significantly reduced in sizewhen compared to the casing or liner previously installed. Commonly,after the installation of each casing or liner, cement slurry is pumpeddownhole and back up into the space or annulus between the casing orliner and the wall of the wellbore, in an amount sufficient to fill thespace. The cement slurry, upon setting, stabilizes the casing or linerin the wellbore, prevents fluid exchange between or among formationlayers through which the wellbore passes, and prevents gas from risingup the wellbore.

The use of a series of liners which have sequentially reduced diametersis derived from long experience and is aimed at avoiding problems at thetime of insertion of casing or liner installation in the wellbore. Thenumber of liners or casings required to reach a given target location isdetermined principally by the properties of the formations penetratedand by the pressures of the fluids contained in the formations. If thedriller encounters an extended series of high pressure/low pressureconfigurations, the number of liners required under such circumstancesmay be such that the well cannot usefully be completed because of thecontinued reduction of the liner diameters required. Again, a furtherproblem of the standard well liner configuration is that large volumesof cuttings are produced initially, and heavy logistics are requiredduring early phases of drilling.

While several approaches to the resolution of these problems have beenattempted, none have proven totally satisfactory. Accordingly, there hasexisted a need for a well lining and cementing technique or procedure,and means to carry it out, which would eliminate or significantly reducethe degree of diameter reduction required when a series of well linersmust be inserted. The invention addresses this need.

SUMMARY OF THE INVENTION

There is thus provided, in one embodiment, a method or process, usefulin cementing a well, especially a hydrocarbon well, which ischaracterized by the use of increased external and internal diameterliners, i.e., by a reduction in the degree of diameter reduction of theliners required, and which does not require excessively large initialconductor casing or surface pipe. Accordingly, in this embodiment, theinvention relates to a method of cementing a wellbore in which a casingor first liner is provided in a wellbore. (As utilized herein, the terms"first" and "second", etc., in relation to the casing or linersmentioned, are relative, it being understood that, after the initial"second" casing or liner is cemented, it may become a "first" liner forthe next cementing operation as such operations proceed down thewellbore.)

Further drilling operations are then conducted to provide an enlargedwellbore. As used herein, the term "enlarged wellbore" refers to awellbore or borehole having a diameter greater than that of the internaldiameter of the casing or preceding liner, preferably greater than theexternal diameter of the casing or preceding liner, such a wellborebeing provided or drilled in a manner known to those skilled in the art,as described more fully hereinafter. At a desired depth, or when it isotherwise decided to line and cement the enlarged wellbore, a secondliner, whose greatest external (outside) diameter approximates, i.e., isonly slightly smaller than the internal diameter of the casing or firstliner provided, is then provided in the enlarged wellbore through thecasing or first liner. The second liner comprises a minor section orsegment of significantly or further reduced external and internaldiameter (in relation to the remaining or remainder segment of thesecond liner) and is composed, at least in said minor section, of adeformable liner material. According to the invention, the second lineris positioned in relation to the enlarged wellbore so that the sectionof reduced external diameter is located or positioned in the lowerportion of the casing or first liner and the remainder segment below thelower portion, in such manner that fluid may circulate freely, i.e.,without substantial or significant impediment, in the annuli formed bythe second liner and the enlarged wellbore and the internal wall of thecasing or first liner.

Inside the bore of the larger remaining or remainder segment of thesecond liner there is disposed or provided, as more fully describedhereinafter, a movable, fluid tight die member of appropriatedimensions, preferably positioned in the second liner distant from thebottom of the remainder segment and proximate the minor section ofreduced external and internal diameter, and which, after initialpositioning or installation in the enlarged wellbore, is fixed inrelation to said wellbore. As utilized herein, the phrase "fluid tight",in reference to the die member, is understood to indicate that the diemember is appropriately sized and shaped and contains appropriatesealing means to prevent significant passage of fluid, even undersubstantial pressure, as described hereinafter, past its periphery orcircumference which is contiguous to the interior wall or bore of theremainder segment of the second liner. The fluid tight die member,including the sealing means, is further a component or element of thenovel die-expansion assembly of the invention which comprises means fortransmitting a fluid to the bore of a liner, and means for connectingthe die member to a drillstring. The latter means are important inpositioning the novel liner-die assembly in the enlarged wellboreinitially, as described more fully hereinafter, and in responding toapplied fluid pressure. As utilized herein, the term "drillstring" isunderstood to include tool members or collars, etc., normally utilizedin wellbore operations. In the specific context of the invention, thedie-expansion assembly comprises means for transmitting a fluid to thebore of the remainder segment of the second liner, to the end that afluid under significant pressure may be applied to the bore of theremainder segment of the second liner, and further comprises means forconnecting the die member to a drillstring.

According to the method of the invention, upon proper positioning of theliner-die assembly of the invention in the wellbore, cement slurry isthen pumped down the drillstring through the casing or first liner andthe second liner (via the means for transmitting a fluid) and into theenlarged wellbore annulus in an amount sufficient to cement the wellboreannulus. After the cement is in place, the bottom or bottom end of thesecond liner is sealed, by standard techniques known to those skilled inthe art, to prevent egress of fluid from the liner. As utilized herein,reference to the "bottom" or "bottom end" of the liner is to beconstrued as referring to a site downhole on or in the liner rather thanas a precise location of the liner body. The sealing of the bottom endof the liner, coupled with the seal provided by the fluid tight diemember, provides or constitutes, assuming a location of the die memberremoved or distant from the bottom of the liner, and, with the exceptionof communication with the aforementioned means for transmitting a fluid,a sealed compartment or recess in the bore of the remainder segment ofthe second liner. Substantial fluid pressure is then applied to theinterior of this sealed remainder segment recess by pumping a fluid,e.g., a wellbore fluid such as a drilling fluid or a spacer fluid,through said means for transmitting a fluid which communicates with thecompartment or recess. As fluid under pressure is introduced into theotherwise sealed recess, the increasing pressure therein tends to forcethe fluid tight die member up the second liner bore. According to theinvention, as fluid pressure is increased in the sealed recess, theposition of the die-expansion assembly, including the die member, ismechanically adjusted or allowed to adjust by translation upward in theliner (and the wellbore). The rate of upward adjustment or movement ofthe die-expansion assembly by upward movement of the running string andthe application of pressure to the second liner bore recess arecorrelated so as to produce movement of the die member up through thesection of reduced diameter with concurrent gradual deformation andexpansion of the section of reduced diameter, providing an expandedsection or segment having an external diameter equal to orapproximating, preferably slightly greater or larger than that of theremainder segment of the second liner, as described more fullyhereinafter. The expansion of the section provides an external diameterfor the section which more closely approximates the internal diameter ofthe casing or first liner, while providing a larger flow passageinternally for production fluids. Continued application of fluidpressure and correlated upward translation or adjustment of the positionof the die-expansion assembly frees the die member from the secondliner, the second liner then being positioned or allowed to remain witha substantial minor portion of the newly expanded segment in the casingor first liner. The cement slurry in the wellbore annulus is thenallowed to set.

In yet further embodiments, the invention relates to a novel liner,which may additionally include expansion means therein; to an apparatusor tool for expansion of a liner having a reduced diameter section; andto a novel liner-die assembly or combination which is useful incementing operations. More particularly, the liner of the inventioncomprises a wellbore liner having a minor section of reduced externaland internal diameter composed of a deformable material and a largerremainder section of increased external and internal diameter. Theexpansion device or apparatus of the invention comprises unique fluidtight die means adapted for expansion of a liner section of reducedinternal and external diameter, and preferably comprises a means fortransmitting a fluid, e.g., a pipe; a die member adapted for expanding,at least substantially uniformly, the bore of a liner, on the peripheryof said pipe; and sealing means positioned on the periphery of the diemember adapted to provide a fluid tight seal between the bore of a linerand said die member. In the preferred arrangement, the pipe is providedat one end thereof with means for connecting the pipe to, or forsuspending the pipe from, a drillstring, and is further preferablyprovided at the opposite end thereof with means for suspending a tool,preferably components used in cementing operations, and, especially, inone aspect of the invention, means to assist in sealing the end of theliner distant from said opposite end of the pipe.

The invention further relates to a novel liner-die assembly. In thisaspect, the invention comprises the novel wellbore liner in which thereis disposed the die-expansion assembly of the invention, as described,the assembly being disposed in said liner with the longitudinal axis ofthe means for transmitting fluid, or pipe, coincident with the axis ofthe liner and the fluid tight die member positioned in the remaindersegment of the liner.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates schematically the prior art practice of telescopingliner sections.

FIG. 2 illustrates schematically a liner and liner assembly according tothe invention.

FIGS. 3 and 4 illustrate sectional views of liner expansion toolsaccording to the invention.

FIGS. 5 through 7 illustrate schematically the pipe expansion method orprocess of the invention.

DETAILED DESCRIPTION OF THE INVENTION

For a fuller understanding of the invention, reference is made to thedrawing. Accordingly, in FIG. 1 there is shown a well string 1 extendingto the earth surface 2 and to conductor pipe or casing 3. Conductor pipe3 is positioned in the portion 4a of wellbore 4, while pipe 5 is inreduced diameter section 4b of the same wellbore. The wellbore formssegmented annulus 6 with pipes 3 and 5, the width of the annulussegments being the same or approximately the same. A further reduceddiameter section 9 is illustrated. As indicated, standard cementingoperations provide a cemented annulus which stabilizes the wellbore, butthe effective diameter of the conducting passage is progressively andsubstantially reduced as the well is deepened.

FIG. 2 illustrates an important aspect of the invention. Accordingly, inFIG. 2 there is shown a liner-die assembly designated generally as 10.The assembly includes the liner component 11 which, as shown, comprisesa liner head section 12 which includes a section of reduced external andinternal diameter coupled to a main body portion or remainder segment13. In a practical case, the external diameter of the section of reducedexternal and internal diameter may be reduced from that of the remaindersegment on the order of two inches or so, with a corresponding decreasein the internal diameter of the reduced diameter section. As will beunderstood by those skilled in the art, a "liner" or "casing" will becomposed of segments or sections assembled and coupled by suitablemeans, such as by threading. In the present invention, the section ofreduced external and internal diameter 12 may be formed in one orcomposed of more than one section of liner, it being recognized that theremainder section or segment will normally comprise many sections (30ft.) to the end or bottom end thereof. Head section 12, which comprisesa deformable material, preferably is connected to the main segment ofthe liner 13 by appropriate threading of the two segments. Alternately,not shown, the head section and a portion of the remainder or main bodysegment may be of integral construction. An elastic or compressiblesleeve (e.g., rubber) or sleeves 12a may be provided on head section 12for stability and sealing. A preferred fluid tight die assembly,indicated generally as 14, and described more fully hereinafter, isprovided. The preferred assembly 14 includes suitable mounting means orconnecting means, such as a threaded connection 15, for connecting to arunning string or other tool, and may be provided with threads or othersuitable connecting means to connect to other tools, e.g., cementingoperation components, indicated generally at 16, such as wiper pluglaunching apparatus, as described, for example, in U.S. Ser. No.08/805,782, filed Feb. 25, 1997, by Gilbert Lavaure, Jason Jonas, andBernard Piot, incorporated herein by reference. Liner segment 13 isprovided with suitable partial sealing means 17, such as a differentialfill-up collar, at or near the end of the liner opposite the suspendingor connecting means, to allow ingress of fluid into the liner duringinsertion thereof in the enlarged wellbore, seal the liner from ingressof fluid from the wellbore after its insertion, and prevent egress offluid from the bore of segment 13 (as described more fully hereinafter).As will be evident to those skilled in the art, a portion of the linercontaining the die assembly may suitably be lowered into a wellbore as aunit, to the purpose that, upon completion of the cementing anddeforming technique described more fully hereinafter, a suitablecemented liner combination of genuine advantage is provided.

FIG. 3 illustrates the simplest form of the die member assembly.Accordingly, there is shown a die member 20 of suitable shape andcomposition, such as hardened steel, and adapted or sized and shaped toexpand a liner section of reduced diameter. Other suitable die formingmaterials are well known, and the particular die member materialutilized is a matter of choice. In the illustration, the die member 20comprises enlarged sections of variable diameter and is of generallyfrustoconical shape provided with suitable beveling in the segment ofthe die member where shaping of the liner section will be initiated,although other deforming shapes of the die member may be provided. Ineach application of the invention, the die member will be shaped ordesigned to provide an at least substantially uniform expanded ordeformed liner segment of circular or approximately circular periphery,the die structure being selected to provide a periphery of the deformedand expanded segment equal to or approximating (slightly larger or lessthan) the periphery of the remainder segment of the liner. As will berecognized by those skilled in the art, die structures are known, forexample, which will deform the reduced diameter segment to provide anexpanded internal periphery slightly larger than that of the die. Thisaspect of the invention is preferred, since there is the possibility ofa virtual force fit of the expanded section in the casing or upperliner.

In this illustration, the die member 20 further comprises a fluid tightseal 21, as previously described, such as a polymer cupseal, for sealingthe die in a liner and allowing sufficient fluid pressure, as describedhereinafter, to produce movement of the die member. The particularsealing material may be selected by those skilled in the art, a widevariety of sealing materials being suitable. For example, rubber orneoprene may also be utilized. The die member is provided with a bore ormeans 22 for transmitting a fluid in its center, and the bore terminatesat both ends thereof with or in connecting means. Thus, threads areprovided at 23 and 24 for connecting the die member to a running stringor a tool, and suspending and/or positioning components, respectively.

A preferred embodiment of the die assembly is illustrated in greaterdetail in FIG. 4. The die assembly shown comprises a pipe or generallytubular body 25 having threaded connecting means or segments 26 and 27(box and pin) for connecting to a running string and suspending a toolor suitable cementing components in a liner, respectively. A die member28 is provided on pipe 25 and is preferably of integral constructiontherewith, being of suitable shape and composition, as described withrespect to FIG. 3, and adapted or sized and shaped in a similar mannerto expand a liner section such as liner section 12. The connectingmeans, in whatever form employed, e.g., as also shown in FIG. 3, thusenables the positioning or adjustment of the position of the die memberin a liner by movement, for example, of a drillstring attached thereto.If not of integral construction, die member 28 may be mounted on pipe 25by suitable mounting means (not shown). In a manner similar to theembodiment of FIG. 3, the die member 28 comprises enlarged sections ofvariable diameter and is of generally frustoconical shape provided withsuitable beveling in the segment of the die member where shaping of theliner section 12 will be initiated, although other deforming shapes ofthe die member may be provided. The die member 28 further comprises afluid tight seal 29, as previously described.

The procedure of the invention and operation of the liner 10 assemblyand die assembly 14 are understood more fully by reference to schematicFIGS. 5 through 7. Elements previously described with respect to FIGS. 1through 4 are referred to by identical numbers. Accordingly, in FIG. 5the liner assembly is provided in a wellbore 30, such as an oil or gaswell bore, and positioned in relation to cemented casing 31, as shown.Wellbore 30 has a diameter greater than the external diameter of casing31, such wellbores being obtainable by use of a bi-center bit,under-reamer bit, or similar tool known to those skilled in the art. Theexternal diameter of liner segment 13 is preferably slightly smallerthan the internal diameter of casing 31, being just sufficiently smallerto allow lowering thereof through casing 31. The liner assembly ispositioned in the enlarged wellbore, as shown, so that fluids, e.g.,drilling mud or cement slurry, may be passed down the string 1 and viathe pipe or bore 25 into the liner segment 13 or suitable tools orstructure therein, described more fully hereinafter, out of the linersegment 13, and into the wellbore annulus 32, and through the annulussegment 33, which is formed by the external wall of section 12 and thelower portion of casing 31. Liner section 12 is formed, as mentioned, ofa deformable liner material, such as a metal, e.g., steel or otheralloy, which is suitable for liner duty. As used herein, the term"deformable" is understood in its common sense as indicating a capacityfor shaping or expansion by suitable application of mechanical pressure.The fluid tight die assembly is positioned or disposed in the liner sothat the longitudinal axes of the pipe and the liner are coincident.Pipe 25 may be of variable length and may or may not extend from liner11. As will be evident to those skilled in the art, the invention isparticularly adapted to use of liners of decreased wall thickness.

As previously mentioned, liner segment 13 is provided with suitablestructure 17, at or near the end of the remainder segment of the liner,disposed from the die assembly, to allow ingress of fluid from thewellbore, such as a displacement fluid, during insertion of the liner,and sealing of the liner from ingress of cement slurry after cementing.In the usual case, a differential fill-up collar will be employed at ornear the bottom of the liner to prevent wellbore fluids from enteringthe liner, and any suitable such collar or similar device may beemployed. A variety of such devices are described in Well Cementing,edited by E. I. Nelson, Schlumberger Educational Services (1990), andthe selection of a particular device is well within the ambit of thoseskilled in the art. Additionally, in order to seal the bottom of theliner after the cement has been placed in the wellbore annulus, as morefully described hereinafter, suitable sealing means, known to thoseskilled in the art, may be provided to prevent egress of fluid from theliner. Preferably, the wiper plug system described in the aforementionedSer. No. 08/805,782 may be employed, to the effect that a fluid tightseal is formed at the end of the liner distant from the assembly, or thebottom of the liner.

In the position shown in FIG. 5, the liner assembly is especiallyadapted to a cementing operation, and hanger elements are not requiredsince the liner assembly may be supported by the string 1. Moreparticularly, following standard cementing procedures, cement slurry maybe pumped downhole through the string 1 and through liner 11 via pipe 25in the die assembly, through flow distributor 16, which may be that ofthe aforementioned wiper plug launching system, and out the bottom ofthe liner through open sealing means 17. The cement slurry displacesdrilling fluid and/or a suitable spacer fluid between the cement slurryand the drilling fluid in the wellbore annulus, the drilling fluidand/or spacer fluid passing from annulus 32 into annulus 33 in casing 31without substantial impediment. The advantage of the reduced crosssection of segment 12, which permits flow of fluids out of the wellbore,is demonstrated at this juncture. Without such feature, the ultimategoal of a wider cross section for production fluids cannot be achievedbecause of the requirement for removal of fluids from the boreholeannulus. Sufficient cement slurry is employed to fill the annulus 32.The invention now provides for expansion of section 12 to provide for alarger diameter cross section corresponding to that of section 13.

As shown in FIG. 6, sealing means 17 (schematically shown) at the bottomof liner section 13 is sealed to the ingress and egress of fluid. In thenormal case, a wiper plug, which is solid, is sent downhole, aftersufficient cement slurry has been sent into annulus 32, to seal, withthe differential fillup collar, the bottom of liner to egress of fluid.As mentioned, the technique of the aforementioned Ser. No. 08/805,782 ispreferred. Fluid pressure is then applied to the bore of the linersegment 13 by pumping a fluid through the pipe 25 into the bore of liner13. Any suitable wellbore fluid or liquid available may be used, e.g., adisplacement fluid, a completion fluid, water, or sea water. The fluidis pumped at sufficient pressure, e.g., 3000 psig, through pipe 25 toprovide upward movement of die member 28 if the member is freed formovement. To this end, the position of the die assembly (including diemember 28) is adjusted or allowed to adjust upward by gradual upwardmovement of the running string 1. Adjustment of the drillstring lengthis made at a rate sufficient to move the die member upward or allowupward movement thereof, caused by the pressure on the die, at acontrolled rate, in response to such continued sufficient application offluid pressure, the continued application of sufficient pressure beingindicated by change in drillstring weight. As continuing sufficientfluid pressure moves die member 28 upward, its movement causes the diemember 28 to expand and shape the deformable liner section 12 so thatthe section diameter and radial cross section thereof equals orapproximates the diameter and radial cross section of the lower section13. Further application of fluid pressure in the bore of liner 11 withcontinued adjustment of the position of die member 28 will free the die28 from the liner 11, as shown in FIG. 7. The result of the deformationoperation is the provision of an upper segment 12 of the liner 11 whichnow corresponds in size to that of lower segment 13. The cement is thenallowed to set, producing a stabilized wellbore with increased flowcapability over conventional liner sequence technique.

While the invention has been described with reference to specificembodiments, it is understood that various modifications and embodimentswill be suggested to those skilled in the art upon reading andunderstanding this disclosure. Accordingly, it is intended that all suchmodifications and embodiments be included within the invention and thatthe scope of the invention be limited only by the appended claims.

What is claimed is:
 1. A method of cementing a wellbore comprisingproviding a casing in a wellbore and drilling a further segment ofenlarged wellbore;providing in the enlarged wellbore, through thecasing, a liner of smaller external diameter comprising a minor sectionof further reduced external and internal diameter composed of adeformable liner material, and a remainder segment having an externaldiameter approximating the internal diameter of the casing, containing amovable fluid tight die member in the bore thereof at a location in thebore distant from the bottom end of said remainder segment, the linerfurther comprising means for transmitting a fluid to the bore of theremainder segment below the fluid tight die member, through the fluidtight die member, the section of reduced external and internal diameterbeing positioned in the lower portion of said casing in such manner, andthe remainder segment of the liner below the lower portion of the casingin the enlarged wellbore, so that fluid may circulate withoutsubstantial impediment in the annuli formed by said liner and theenlarged wellbore and casing; pumping a cement slurry down the casingand through the liner, and into the wellbore annulus in an amountsufficient to cement said wellbore annulus; sealing the bottom of theremainder segment of the liner; transmitting a fluid to and applyingsufficient fluid pressure to the bore of the remainder segment of theliner below the fluid tight die member to move the die member up theliner and expand said minor section, and allowing said fluid tight diemember to move up the wellbore to provide an external diameter of theminor section equal to or approximating that of the remainder segment ofthe liner; and removing the fluid tight die member from the expandedminor section and allowing the cement to set.
 2. A method of cementing awellbore comprisingproviding a first liner in a wellbore and drilling afurther segment of enlarged wellbore; providing in the enlargedwellbore, through the first liner, a second liner of smaller externaldiameter comprising a minor section of further reduced external andinternal diameter composed of a deformable liner material, and aremainder segment having an external diameter approximating the internaldiameter of the liner, containing a fluid tight die member in the borethereof, at a location in the bore distant from the bottom end of saidremainder segment, the liner further comprising means for transmitting afluid to the bore of the remainder segment below the fluid tight diemember, through the fluid tight die member, the section of reducedexternal and internal diameter being positioned in the lower portion ofsaid first liner in such manner, and the remainder segment of the secondliner below the lower portion of the first liner in the enlargedwellbore, so that fluid may circulate without substantial impediment inthe annuli formed by said liner and the enlarged wellbore and firstliner; pumping a cement slurry down the first liner and through thesecond liner, and into the wellbore annulus in an amount sufficient tocement said wellbore annulus; sealing the bottom of the remaindersegment of the second liner; transmitting a fluid to and applyingsufficient fluid pressure to the bore of the remainder segment of thesecond liner below the fluid tight die member to move the die member upthe liner and expand said minor section, and allowing said fluid tightdie to move up the wellbore to provide an external diameter of the minorsection equal to or approximating that of the remainder segment of theliner; and removing the fluid tight die member from the expanded minorsection and allowing the cement to set.
 3. An improved wellbore linerfor ameliorating subsequent casing diameter reduction, comprising asection of reduced external and internal diameter composed of adeformable liner material and a larger remainder segment of increasedexternal and internal diameter, and a fluid tight die member disposed inthe bore of the remainder segment, wherein the fluid tight die membercomprises a means for transmitting a fluid therethrough, and comprisinga means for sealing an end of said liner at a location removed from thefluid tight die member.
 4. Apparatus comprising a die member adapted forexpanding, at least substantially uniformly, the bore of a liner;sealingmeans positioned on the periphery of said die member adapted to providea fluid tight seal between the bore of a liner and said die member;means for transmitting a fluid through the die member; means forconnecting the die member to a drillstring; and means for suspending atool from the die member.
 5. Apparatus comprising a pipe, a die memberadapted for expanding, at least substantially uniformly, the bore of aliner, on the periphery of said pipe, and sealing means positioned onthe periphery of said die member adapted to provide a fluid tight sealbetween the bore of said liner and said die member.
 6. The apparatus ofclaim 5 wherein the pipe is provided at one end thereof with means forconnecting the pipe to a drillstring.
 7. Apparatus comprising a pipe, adie member adapted for expanding, at least substantially uniformly, thebore of a liner, on the periphery of said pipe, and sealing meanspositioned on the periphery of said die member adapted to provide afluid tight seal between the bore of said liner and said die member, andwherein said pipe is provided at one end thereof with a means forconnecting the pipe and at the opposite end thereof, a means forsuspending a tool.
 8. A wellbore liner for ameliorating subsequentcasing diameter reduction associated with subterranean drillingoperations comprising(a) a section of reduced external and internaldiameter composed of a deformable liner material and a larger remaindersegment of increased external and internal diameter; (b) a fluid tightdie assembly disposed in said liner, said assembly comprising a fluidtight die member including a sealing means on the periphery of a pipe,the assembly disposed in said liner with the longitudinal axis of thepipe coincident with the axis of the liner and the fluid tight diemember positioned in the remainder segment of the liner.
 9. A wellboreliner comprising a section of reduced external and internal diametercomposed of a deformable liner material and a larger remainder segmentof increased external and internal diameter, and at least one sleevecomposed of a compressible material mounted on the periphery of thesection of reduced external and internal diameter.
 10. The liner ofclaim 9 in which the compressible material is rubber.
 11. A method ofcementing a wellbore comprising providing a casing in a wellbore anddrilling a further segment of enlarged wellbore;providing in theenlarged wellbore, through the casing, and connected to a drillstring, aliner of smaller external diameter comprising a minor section of furtherreduced external and internal diameter composed of a deformable linermaterial, and a remainder segment having an external diameterapproximating the internal diameter of the casing, containing a movablefluid tight die member in the bore thereof at a location in the boredistant from the bottom end of said remainder segment, the liner furthercomprising means for transmitting a fluid to the bore of the remaindersegment below the fluid tight die member, through the fluid tight diemember, the section of reduced external and internal diameter beingpositioned in the lower portion of said casing in such manner, and theremainder segment of the liner below the lower portion of the casing inthe enlarged wellbore, so that fluid may circulate without substantialimpediment in the annuli formed by said liner and the enlarged wellboreand casing; pumping a cement slurry down the casing and through theliner, and into the wellbore annulus in an amount sufficient to cementsaid wellbore annulus; sealing the bottom of the remainder segment ofthe liner; transmitting a fluid to and applying sufficient fluidpressure to the bore of the remainder segment of the liner below thefluid tight die member to move the die member up the liner and expandsaid minor section, and moving said fluid tight die member up thewellbore in response to continued sufficient fluid pressure by adjustingthe position of the drillstring upward, to provide an external diameterof the minor section equal to or approximating that of the remaindersegment of the liner; and removing the fluid tight die member from theexpanded minor section and allowing the cement to set.
 12. The method ofclaim 11 wherein the well is a hydrocarbon well.